In the past three years, Mary has secured the acquittal of the youngest person in the United Kingdom to be accused of terrorism. She represented the stepmother of Arthur Labinjo-Hughes at her trial for murder and cruelty and successfully argued at the Court of Appeal that her sentence was not unduly lenient. She secured the acquittal of the alleged leader of a significant organised crime group who was said to run the sale and supply of drugs and firearms in the Coventry area of the Midlands by violence and threats. She secured the conviction on retrial of Emma Magson and the conviction of John Jefferies who killed two young men in revenge for damaging his car. In addition, she has secured the conviction for murder of the parents of Finley Boden for his savage death.

When defending she regularly visits her clients, gains their trust and determines a focused trial strategy. Mary is fearless when cross-examining those who require a robust approach.



Mary is a powerful and compelling advocate whose emotional intelligence and empathy give her a real tactical advantage, whether she prosecutes or defends. She is 100% committed to her cases, and her work is outstanding. Particularly good at questioning vulnerable witnesses. Legal 500 2023
Mary demonstrates an impressive grasp for evidence and her presentation of the case for the Crown is excellent. She brings the threads of a case together with great skill and prosecutes fairly and confidently in order to achieve justice for all involved. Legal 500 2022
Extremely robust and meticulous in her case preparation and cross-examination, commanding the respect of the court room and instilling confidence in her.Legal 500 2021
Tenacious, focused and secures excellent outcomes.Legal 500 2020
I wish to take the opportunity to thank Mary Prior QC for her tireless work on this case. This was a case that involved various levels of professionalism, whether it was dealing with demanding solicitors, a vulnerable defendant or their family. Mary Prior QC excelled in dealing with everyones expectations whilst remaining professional throughout. Congratulations and thank you Mary Prior QC.Solicitor

Further information

Appointed KC 2017

Bencher at Gray’s Inn

Vice Chair of the Criminal Bar Association

Deputy Head of the Criminal Team

36 Crime Vice Chair of Education – Outreach – Gray’s Inn

Chair of RASSO Group CBA Vulnerable Witness trainer/facilitator ICCA

Gray’s Inn advocacy and ethics trainer

Women in Criminal Law – Joint Chair Midlands Branch

Trainer for Leicestershire Police disclosure champions

Co-Chair Leicestershire Schools Courts Competition

Member of:
Midland Circuit South Eastern Circuit Criminal Bar Association

Gray’s Inn Visiting professional fellow Aston University

Editorial Board The Contemporary Law Forum – India

Women in Criminal Law

Patron of Bristol University Criminal Justice Society

Patron of Northumbria Bar Society Trustee of Bringing (Dis) Ability to the Bar

Champion of Neurodiversity in Law

Patron of the Non-Russell Group of Lawyers